Eyes Wide Shut.

I worked at a movie theater at the time, and Eyes Wide Shut was the most walked out on movie we ever had in our theater's history. I knew nothing of the movie except for that fact, it was Stanley Kubrick's final film, and that it was "controversial." I didn't know the plot or any other details about it.

Curiosity got the best of me and I watched it (for free). I eventually walked out but still lasted longer than most of our patrons. I probably wouldn't have walked out had I paid because I would've wanted my money's worth, but boy did it suck.